Heating press and method for vulcanizing a vehicle tire in said heating press under vacuum

ABSTRACT

A heating press (1) for vulcanizing a vehicle tire under a vacuum,comprising a heating press upper part (3) and a heating press lower part (6), wherein a container (2) having the mold parts (14, 16, 17, 18, 21) of a segmented vulcanizing mold and a cylindrical hood upper part (4) enclosing said container are arranged on the heating press upper part (3),wherein the hood upper part (4) and the heating press upper part (3) can be moved independently of one another and relative to one another in the axial direction (P1),wherein the cylindrical hood upper part (4) has a length (23) which is sufficient to form a closed hood interior space (12) with the heating press lower part (6) and heating press upper part (4) when the heating press upper part (3) is open,wherein at least one respective vacuum-tight seal (5) is arranged on those surfaces at which the hood upper part (4) directly adjoins the heating press upper part (3) and—when the hood interior space (12) is closed—the heating press lower part (6), in order to make the closed hood interior space (12) sealable in a vacuum-tight manner,wherein, in the course of a first stroke (H1), the hood upper part (4) can be moved independently of the heating press upper part (3) in the axial direction P1 in such a way,wherein, in the course of a second stroke (H2), the heating press upper part (3) can be moved independently of the hood upper part (4) in the axial direction P1 in such a way that the vulcanizing mold can be completely closed under vacuum conditions in the interior space of the hood (12).

The invention relates to a heating press for vulcanizing a vehicle tire,comprising a heating press upper part and a heating press lower part,wherein a container having the mold parts of a vulcanizing mold and acylindrical hood upper part enclosing said container are arranged on theheating press upper part, and wherein the heating press upper part andthe heating press lower part are connected to the container in such away that, when the heating press upper part is being lowered through astroke that takes place in the axial direction, the mold parts of thevulcanizing mold can be closed in the radial direction. The inventionfurthermore relates to a method for vulcanizing a green tire in thisabovementioned heating press.

The above-described heating press is a standard heating press forvulcanizing vehicle tires under atmospheric conditions.

The heating press comprises a so-called container which comprises theactual segmented vulcanizing mold with the mold segments and sidewallshells and bead rings, which mold the tire. Furthermore, heatingchambers are provided for controlling the temperature of the moldingparts. During the vulcanization, the container is surrounded by a closedhood which, in the prior art, serves primarily for temperatureinsulation during the vulcanization.

In order to as far as possible avoid defects on the tire surface, theair between the surface of the green tire and the shaping surface of themold parts of the vulcanizing mold must be removed. For this purpose, itis generally known for 1000 to 5000 ventilation valves to be provided inthe mold parts. By means of these ventilation valves, the air from themold cavity is discharged radially and axially outward throughventilation channels. However, the mold parts of a new vulcanizing moldhave to be equipped with these valves. Furthermore, these valves tend tobecome dirty owing to rubber that ingresses from the tire forvulcanization, such that said valves have to be exchanged or cleaned,which requires great outlay.

The invention is based on the object of providing a heating press forvulcanizing a vehicle tire, with which vehicle tires can be reliablyvulcanized without the need for ventilation valves in the vulcanizingmold. The object of the invention is likewise to provide a method forvulcanizing a vehicle tire in an efficient manner in terms of time bymeans of the heating press mentioned above.

The object is achieved in relation to the heating press in that

-   -   the hood upper part and the heating press upper part can be        moved independently of one another and relative to one another        in the axial direction,    -   the cylindrical hood upper part has a length which is sufficient        to form a closed hood interior space with the heating press        lower part and heating press upper part when the heating press        upper part is open,    -   at least one respective vacuum-tight seal is arranged on those        surfaces at which the hood upper part directly adjoins the        heating press upper part and—when the hood interior space is        closed—the heating press lower part, in order to make the closed        hood interior space sealable in a vacuum-tight manner, wherein        the seals are preferably arranged on the heating press upper        part and on the heating press lower part,    -   in the course of a first stroke, the hood upper part can be        moved independently of the heating press upper part in the axial        direction in such a way that said hood upper part forms a        vacuum-tight hood interior space with the heating press lower        part, although the vulcanizing mold remains open in an        air-permeable manner,    -   a pump and a vacuum tank, by means of which a vacuum can be        generated in the interior space of the hood after the first        stroke, are provided, wherein the vacuum tank and the pump are        connected to the interior space of the hood, and wherein the        vacuum tank and the pump are connected to one another, and    -   in the course of a second stroke, the heating press upper part        can be moved independently of the hood upper part in the axial        direction in such a way that the vulcanizing mold can be        completely closed under vacuum conditions in the interior space        of the hood.

It is essential that the heating press according to the invention isused to vulcanize vehicle tires under vacuum. The vulcanizing molditself does not have any ventilation means for ventilating the moldcavity. The 1000 to 5000 ventilation valves arranged in the vulcanizingmold in the prior art, through which ventilation valves the air from themold cavity is discharged radially to the outside, are omitted by virtueof the vulcanization being performed under a vacuum. In this way,post-processing of the rubber flash that is formed on the tire by theventilation means, and an exchange and/or cleaning of ventilation valvesthat are no longer functional, are no longer necessary. These aretime-consuming and expensive. Furthermore, by virtue of thevulcanization being performed under a vacuum, the vulcanized tire takeson an external form which is absolutely free from defects and is thus ofperfect appearance.

The vacuum that can be obtained inside the closed hood interior spaceafter the first stroke of the hood upper part serves to remove the airfrom the not-yet closed vulcanizing mold, in particular between theouter surface of the tire and the mold surfaces of the molding parts ofthe vulcanizing mold. After the second stroke of the heating press upperpart, which takes place under vacuum conditions in the hood interiorspace, the vulcanizing mold can be completely closed. The tire forvulcanization can be manufactured with high quality and without defects.In this respect, in order to form the vacuum-tight hood interior space,in one embodiment of the invention the end face of the hood upper partcan move onto the heating press lower part or, in another embodiment ofthe invention, it can be moved over the heating press lower part, withthe result that the end of the hood upper part encloses the heatingpress lower part.

Of course, to obtain a vacuum-tight hood interior space, the hood orheating press can have further seals. It is explicitly the intentionthat no modifications with regard to measures for providingvacuum-tightness be made to the container or to the vulcanizing molditself.

The term “vacuum” refers to air pressure in the range from 950 mbar(abs) to mbar (abs).

The ring seal preferably has a circular or polygonal cross section.

It is expedient if a hydraulic, pneumatic or electric actuator, whichcan move the hood upper part in the axial direction, is provided.

In a certain embodiment of the invention, a hood lower part in the formof a circular ring is arranged on the heating press lower part, whereinthe circular ring of the hood upper part and the circular ring of thehood lower part have the same inside diameter and the same outsidediameter and are arranged in line with one another in the heating press.This results in very reliable sealing of the hood interior space.

It is expedient if the seals are ring seals with circular, polygonaland/or flat cross sections.

It is expedient for reliable sealing if the ring seal is arranged in acircular-ring-shaped groove, wherein the diameter of the ring seals isslightly greater than the depth of the groove. Slightly greater meansthat the seal, when installed into the groove and in the sealing state,is compressed by at most 40% in relation to the compression-freegeometry of the seal. Through the exact design of the groove in relationto the seal geometry, damage to the seal(s) is additionally preventedand durability is improved.

In one embodiment of the invention, the ring seals consist of solidmaterial. The solid material may consist of one or more materials thatare known for seals, such as FKM or FFKM. These seals are inexpensiveand easy to handle.

In another embodiment of the invention, the ring seal is a hose ofvariable diameter. This has the advantage that less load is exerted onthe ring seal, and said ring seal is enlarged in terms of diameter onlywhen the sealing action is necessary.

It is advantageous if the ring seals are differentially inflated doublering seals. This has the advantage that any leakage can be compensatedwith low levels of pump power.

It is expedient if the vacuum tank has a volume that is approximately 5to 10 times greater than the volume of the closed hood (including mold,container, green tire, heating bellows). It is hereby ensured that avacuum can be reliably generated in the hood. Furthermore, the timerequired for the generation of the required vacuum is significantlyreduced. This may take place in the course of the normal loading andunloading process.

With regard to the method with an abovementioned heating press, theinvention is achieved in that the following steps are performed insuccession:

-   -   a) loading the opened heating press by placing the green tire        for vulcanization into the container,    -   b) moving the hood upper part through a first stroke in the        axial direction toward the heating press lower part, until a        closed hood interior space composed of hood upper part, heating        press upper part and heating press lower part is obtained, while        the vulcanizing mold remains open,    -   c) only if the ring seal is a hose of variable diameter:        inflating the circular-ring-shaped hose seal in order to seal        off the hood interior space in a vacuum-tight manner,    -   d) opening the connection between the vacuum tank and the hood        interior space in order to generate a partial vacuum, by way of        pressure equalization between the vacuum tank and the hood        interior space, in the hood interior space that has been closed        in a vacuum-tight manner,    -   e) when the partial vacuum is obtained in the hood interior        space: closing the connection between the vacuum tank and the        hood interior space, opening the connection between the hood        interior space and the pump, and pumping the remaining air out        of the hood interior space in order to generate the vacuum,    -   f) moving the heating press upper part through a second stroke,        in the course of which the container is moved in such a way that        the vulcanizing mold is completely closed, and subsequently        closing the connection between the hood interior space and the        pump,    -   g) vulcanizing the green tire and opening the connection between        the pump and the vacuum tank and generating a vacuum in the        vacuum tank, wherein the connection of the pump to the hood        interior space and the connection of the vacuum tank to the hood        interior space are each closed,    -   h) opening the heating press by moving the hood upper part and        the heating press upper part and removing the fully vulcanized        tire, and repeating the steps a)-h) in order to vulcanize each        further tire.

It is advantageous if, to facilitate step h), this is preceded by afurther valve arranged in the hood being opened in order to deplete thevacuum in the hood and subsequently being closed again.

An exemplary embodiment of a heating press and the method for vacuumvulcanization of a pneumatic vehicle tire, together with furtheradvantages, will be described on the basis of the following twoschematic figures. In the figures:

FIG. 1 shows a heating press according to the invention with a containerin an open state;

FIG. 2 shows the heating press of FIG. 1 in the closed state.

FIG. 1 shows a heating press 1 according to the invention with acontainer 2 in an open state. The hood upper part is in its initialposition. The green tire can be placed into the heating press 1.

The heating press 1 comprises a heating press lower part 6 and a heatingpress upper part 3 with a cylindrical hood upper part 4 and has thecorresponding mechanisms for positioning the tire for vulcanization, foractuating the constituent parts of the vulcanizing mold, for introducingthe heating media, and for removing the fully vulcanized tire. In theinterior space of the hood upper part 4, a container 2 is arranged onthe heating press upper part 3 in such a way that, when the heatingpress upper part 3 is being moved in the axial direction P1, the moldparts of the vulcanizing mold that are arranged in the container can bemoved in the radial direction P2.

What is provided is a “central mechanism” 8, to which a heating bellows(not illustrated) that can be placed into the green tire (notillustrated) is fastened. Furthermore, nozzles (not illustrated) arearranged on the central mechanism 8, through which nozzles a heatingmedium can be introduced into the heating bellows (not illustrated).

The hood upper part 4 and the heating press upper part 3 can be movedindependently of one another and relative to one another in the axialdirection P1. The cylindrical hood upper part 4 has a length 23 which issufficient to form a closed hood interior space 12 with the heatingpress lower part 6 and heating press upper part 3 when the vulcanizingmold is still open, that is to say when the heating press upper part 3has not been moved completely onto the heating press lower part 6.

The hood upper part 4 is airtight, or vacuum-tight, and in the closedstate forms a vacuum-tight hood interior space 12. In order to seal theend face 7 of the hood upper part 4 in a vacuum-tight manner in theclosed state, a ring seal 5 with a flat cross section is arranged on theheating press lower part 6 where the end face 7 of the hood upper part 4rests against the heating press lower part 6 in the closed state of thehood. A further ring seal 5 is mounted on the heating press upper part 3where the hood upper part 4 directly adjoins the heating press upperpart 3. Further ring seals 9 seal off at least the central mechanism 8with respect to the hood interior space 12 in a vacuum-tight manner.

The container 2 is a conventional container 2 that is already known inthe prior art.

The container 2 contains the segmented vulcanizing mold with a lowerheating plate 13, a lower sidewall shell 14, an upper heating plate 15,an upper sidewall shell 16, a lower bead ring 17 and an upper bead ring18. Those constituent parts of the vulcanizing mold that are moved in avertical (=axial) direction (arrow P1) for the purposes of opening andclosing include the segment ring 19, composed of seven to nine segmentshoes 20, and the profile/mold segments 21 fastened thereto and also theupper sidewall shell 16 with the upper bead ring 18. The segment shoes20 are moved apart radially, in the direction of the arrow P2, to closeand open the vulcanizing mold. On the upper heating plate 15, there isarranged a closing ring 22 which has a beveled inner surface whichinteracts with beveled outer surfaces of the segment shoes 20 of thesegment ring 19 such that, during the closing of the vulcanizing mold,the segment shoes 20 are moved together in a radial direction to formthe closed segment ring 19. In the lower heating plate 13, the upperheating plate 15 and in the closing ring 22, there are incorporatedheating chambers into which at least one heating medium, in particularsaturated steam (water vapor), is introduced for the vulcanization ofthe tire. In this way, the green tire (not illustrated) is heated fromthe outside via the segment shoes 20, the sidewall shells 14, 16 and thebead rings 17, 18, such that this heating is commonly referred to asexternal heating.

A conventional heating bellows (not illustrated) is provided in a knownmanner and is filled with at least one pressurized heating medium inorder to center the green tire in the mold from the inside, wherein theheating bellows is brought into a toroidal shape conforming to a tire.Since the green tire is heated by means of the heating bellows from theinside, this type of heating is referred to as internal heating.

In the course of a first stroke H₁—not illustrated in the figures—thehood upper part 3 can be moved independently of the heating press upperpart 3 in the axial direction P1 by means of an actuator 24 in such away that said hood upper part forms a vacuum-tight hood interior space12 with the heating press lower part 6, although the vulcanizing moldremains open in an air-permeable manner.

With the first stroke H₁ performed by the hood upper part 4, however,the heating press upper part 3 can also be moved at the sametime—although the vulcanizing mold must still remain open after thefirst stroke H₁.

A pump 10 and a vacuum tank 11, by means of which a vacuum can begenerated in the interior space 12 of the hood after the first strokeH₁, are provided. The vacuum tank 11 and the pump 10 are connected tothe interior space 12 of the hood and the vacuum tank 11 and the pump 10are connected to one another. By virtue of a vacuum being provided inthe hood interior space (=interior space of the hood) 12, in particularduring the molding and the vulcanization of the tire, conventionalventilation valves arranged in the mold face of the vulcanizing mold areomitted entirely.

FIG. 2 shows the heating press 1 of FIG. 1 in the closed state, which isobtained after a second stroke H₂, in the course of which the heatingpress upper part 3 can be moved independently of the hood upper part 4in the axial direction P1 such that the vulcanizing mold can becompletely closed under vacuum conditions in the interior space 12 ofthe hood. The connection between the vacuum tank 11 and the hoodinterior space 12 is closed. Then, the connection between the hoodinterior space 12 and the pump 10 is closed. The green tire isvulcanized.

In the case of a passenger motor vehicle tire, the vulcanization thereoftakes approximately 15 minutes. During this time, the connection betweenpump 10 and vacuum tank 11 is opened in order to generate a vacuum inthe vacuum tank 11, wherein the connection of the pump 10 to the hoodand the connection of the vacuum tank 11 to the hood are each closed.After the vulcanization of the tire is complete, the volume of the hoodinterior space 12 is aerated via a valve (not illustrated), and theheating press 1 is opened in order to unload the fully vulcanized tirefrom the container 2 having the vulcanizing mold. For this purpose, theheating press upper part 3 with the container 2 and the hood upper part4 moves upward, and the profile segments 21 simultaneously move outwardin the radial direction P2. The tire is released.

LIST OF REFERENCE SIGNS (Part of the Description)

-   -   1 Heating press    -   2 Container    -   3 Heating press upper part    -   4 Hood upper part    -   5 Ring seal    -   6 Heating press lower part    -   7 End face of the hood upper part    -   8 Central mechanism    -   9 Ring seal    -   10 Pump    -   11 Vacuum tank    -   12 Interior space of the hood=hood interior space    -   13 Lower heating plate    -   14 Lower sidewall shell    -   15 Upper heating plate    -   16 Upper sidewall shell    -   17 Lower bead ring    -   18 Upper bead ring    -   19 Segment ring    -   20 Segment shoe    -   21 Profile segment/mold segment    -   22 Closing ring    -   23 Length of the hood upper part    -   24 Actuator    -   H₁ First stroke    -   H₂ Second stroke    -   P1 Axial direction    -   P2 Radial direction

1-11. (canceled)
 12. A heating press for a tire, the heating presscomprising: a heating press upper part; a heating press lower part; acircular-ring-shaped hood upper part of a hood, the hood upper parthaving a container and mold parts movable in an axial direction (P1) toform a closed hood interior space; a press plate arranged above thecontainer in the hood upper part and moveable in the axial direction(P1); a seal mechanism to establish vacuum-tightness between the heatingpress upper part and the heating press lower part, the seal mechanismhaving nozzles to introduce a heating medium into heating bellows; apump to generate a vacuum in the closed hood interior space; a segmentedvulcanizing mold within the container; the mold configured to be filledwith a pressurized heating medium for a green tire and heated byinternal heating; the heating press upper part moves for a first stroke(H1); and the press plate moves to completely close the vulcanizing moldunder the vacuum for a second stroke (H2). the hood upper part and theheating press upper part can be moved independently of one another andrelative to one another in the axial direction (P1), the cylindricalhood upper part has a length to form a closed hood interior space withthe heating press lower part and heating press upper part when theheating press upper part (3) is open; in the course of the first stroke(H1), the hood upper part can be moved independently of the heatingpress upper part in the axial direction P1 in such a way that said hoodupper part forms a vacuum-tight hood interior space with the heatingpress lower part, although the vulcanizing mold remains open in anair-permeable manner, in the course of a second stroke (H2), the heatingpress upper part can be moved independently of the hood upper part inthe axial direction P1 that the vulcanizing mold can be completelyclosed under vacuum conditions in the interior space of the hood. 13.The heating press of claim 12, wherein a hydraulic, pneumatic orelectric actuator (24), which can move the hood upper part (4)independently of the heating press upper part (3) in the axial direction(P1), is provided.
 14. The heating press of claim 12, wherein a hoodlower part in the form of a circular ring is arranged on the heatingpress lower part (6), wherein the circular ring of the hood upper part(3) and the circular ring of the hood lower part have the same insidediameter and the same outside diameter and are arranged in line with oneanother in the heating press (1).
 15. The heating press of claim 12,wherein the seals are ring seals (5, 9) with circular, polygonal and/orflat cross sections.
 16. The heating press of claim 15, wherein the ringseal (5, 9) is arranged in a circular-ring-shaped groove, wherein thediameter of the ring seal (5, 9) is slightly greater than the depth ofthe groove.
 17. The heating press of claim 15, wherein the ring seal (5,9) consists of solid material.
 18. The heating press of claim 15,wherein the ring seal (5, 9) is a hose of variable diameter.
 19. Theheating press of claim 15, wherein the ring seal (5, 9) is adifferentially inflated double ring seal.
 20. The heating press of claim12, wherein the vacuum tank (11) has a volume that is approximately 5 to10 times greater than the volume of the closed hood(s) (4).
 21. A methodfor vulcanizing a pneumatic vehicle tire under a vacuum in a heatingpress (1), the method comprising: a) loading the opened heating press(1) by placing the green tire for vulcanization into the container (2),b) moving the hood upper part (4) through a first stroke (H1) in theaxial direction (P1) toward the heating press lower part (6), until aclosed hood interior space (12) composed of hood upper part (4), heatingpress upper part (3) and heating press lower part (6) is obtained, whilethe vulcanizing mold remains open, c) only if the ring seal (5, 9) is ahose of variable diameter: inflating the circular-ring-shaped hose sealin order to seal off the hood interior space (12) in a vacuum-tightmanner, d) opening the connection between the vacuum tank (11) and thehood interior space (12) in order to generate a partial vacuum, by wayof pressure equalization between the vacuum tank (11) and the hoodinterior space (12), in the hood interior space (12) that has beenclosed in a vacuum-tight manner, e) when the partial vacuum is obtainedin the hood interior space (12): closing the connection between thevacuum tank (11) and the hood interior space (12), opening theconnection between the hood interior space (12) and the pump (10), andpumping the remaining air out of the hood interior space (12) in orderto generate the vacuum, f) moving the heating press upper part (3)through a second stroke (H2), in the course of which the container (2)is moved in such a way that the vulcanizing mold is completely closed,and subsequently closing the connection between the hood interior space(12) and the pump (10), g) vulcanizing the green tire and opening theconnection between the pump (10) and the vacuum tank (11) and generatinga vacuum in the vacuum tank (11), wherein the connection of the pump(10) to the hood interior space (12) and the connection of the vacuumtank (11) to the hood interior space (12) are each closed, h) openingthe heating press (1) by moving the hood upper part (4) and the heatingpress upper part (3) and removing the fully vulcanized tire, andrepeating the steps a)-h) in order to vulcanize each further tire. 22.The method of claim 21, further comprising arranging a further valve inthe hood in order to deplete the vacuum prior to opening the heatingpress.